Cavity joint



July 19, 194-9. c, OKRESS 2,476,621 CAVITY JOINT Filed NOV. 6, 1942 BYW WWL ATTohNEY Patented July 19, 1949 2,476,621 CAVITY JOINT Ernest C. Okress, Montclair, N. assignor to Westinghouse Electric Corporation, East Pittsburgh,'Pa., a corporation of Pennsylvania Application November 6, 1942, Serial No. 464,824

This invention relates to cavity joints and more particularly to joints between hollow instrumentalities such as sections of wave guides or between a wave guide and a generator the outlet of which is of hollow character.

The use of wave guides for purpose of transfer of radio or ultra high frequency energy from.

place to place is an accepted fact. It is, however,

important that there be surface continuity, from.

an electrical viewpoint, in the entire wave guide from the generator to the instrument to which the energy is being conveyed. Screw threaded joints are generally inefficient when used in lines conveying R. F. currents. Prior practice has been to obtain surface continuity by soldering or otherwise definitely sealing all joints. That procedure is satisfactory for the electrical conductivity requirements, but has its deficiencies from practical considerations. Principal among the short-comings of the prior art is the difficulty involved in making changes, additions and substitutions in the assembly. Another adverse condition encountered in the prior art is the frequent situations encountered making access to joints for obtaining a good soldering thereof ex-- tremely difiicult.

The present invention accordingly has for its general object the provision of an improved, effective and efiicient joint.

Likewise, from a broad aspect, an object of the invention is to provide a cavity joint which is readily assembled or completed and readily disconnected when desired.

More specifically, an object of the invention is to provide a cavity joint which obtains desired electrical continuity with threaded connections obtaining the mechanical connection.

Another object of the invention is to provide a structure enabling the generator or other instrumentalities connected to the wave guide, as well as parts of the wave guide itself to be readily removable and replaceable.

A further object of the invention is to reduce to a minimum reflection of the wave energy due to its presence in the guide.

Still further objects of the invention will appear as the description progresses, both by direct reference thereto and by implication from the context.

Referring to the accompanying drawing in which like numerals of reference indicate similar parts throughout the several views:

Figure 1 is a vertical-longitudinal section of a coupling and associated parts of a wave guide;

7 Claims. (Cl. 178-44) """surrounded or girdled by an outer body portion.

. b 2 Figure 2 is a cross section on line II-H of Fig.

1 looking in the direction indicated;

Figure 3 is a longitudinal section on line III-III of Fig. 1;

Figures 4 and 5 are perspective views of the two portions of which one of the complementary. coupling members. is composed in the present showing; and

Figure 6 is a sectional View on line VI-VI looking in the opposite direction from Fig. 2, as indicated by the arrows.

In the specific embodiment of the invention illustrated in said drawing, the reference numerals l0 and II designate alined sections of a wave guide or other hollow instrumentalities to be,

coupled together both mechanically and electrically. For simplification of description future reference herein will be to the illustrated use of wave guide sections, but it will be understood that the invention is applicable to other instru-- mentalities and the reference to wave guides is not to be construed as limiting, but rather as exemplary.

Generally speaking, the substantially abutting endsof the wave guide sections or other instrumentalities are mechanically coupled by complementary members l2, [3 on the ends of eachsection, with a clamping ring completing the. assembly. More in detail, one said member I2,

provides an inner body portion l5 peripherally I 6, all of suitable metal, such as brass. Thesaid inner member is of generally rectangular configuration the several sides of which are paralv lel to corresponding sides of the wave guide section and all equally spaced from the nearest side thereto of the wave guide. The said inner body portion is provided with a rectangular opening I! therethrough for inclusion of the end margin' of the wave guide section therein, it being prefer- "able to make the endedge of the wave guide flush with the adjacent end face l8 of the body portion I 5. Rectangular opening I1 is made to fit the wave guide, and after said body portion is slid onto and properly positioned on the wave guide with the forward face flush with the end of the wave guide, it is permanently secured as by a fillet of solder l9 at the rearward junction therebetween.

The peripheral edge of the inner body portion I5 is of stepped formation, that is, next the rearward end of the said body portion the peripheral edge has a band-like shoulder 20 therearound. Outer body portion It has an opening 2| therethrough of equal cross-sectional dimensions as the outer cross-sectional dimensions of said shoulder so as to fit thereon. As the crosssectional dimensions of opening 2| remain constant for the entire length of the opening while the cross-sectional dimensions of the inner member are less at the part forward from said shoulder 29, a continuous slot 22 is thereby provided between saidv sections peripherally of the inner section and opening forwardly but not rearwardly. For purpose hereafter set forth, the slot 22 is approximately a quarter-wave length deep referring to the wave length in a rectangular coaxial cable. The two body portions are unified after assembly by suitable means such as a head of solder 23 over the junction line therebetween at the rear faces, thereby constituting said portions a unitary member l2.

It may now be called to attention that the forward face of said member l2 composed of portions l5, l6 above described, is perpendicular to the centerline or length of the wave guide. This means that slot 22 between said body portions is perpendicular to said forward face and substantially parallels and is evenly spaced from the nearest portion of the wave guide wall. Looking toward the face, the slot has a rectangular configuration preferably with rounded corners. The outer peripheral surface of the outer body section is shown cylindrical with a radiating flange 24 at the forward end forming appropriate clamplng engagement for an inwardly directed flange of clamping ring I4.

Complementary member IQ of the coupling is shown as disc-shaped with screw threads at its periphery to cooperate with corresponding threads in the clamping ring. Said disc-shaped complementary member l3 has a central rectangular opening 25 which fits. over the end margin of wave guide section H and secured thereto by a fillet of solder 26.

The inwardly facing fiat surface of complementary member i3 is maintained in spaced parallel relation to forward flat face ill of member i2, this being shown accomplished by provision of a forwardly directed ridge 2'! integrally formed withthe outer body portionlS of, member I3. Said ridge is preferably next the rectangular opening 2! through said portion it so the inside periphery of the ridge is a continuation of the surface of said opening of the body portion. The ridge, by preference, spaces the addressed faces of the complementary members a distance apart forming 'a gap 28 having a width substantially equal to width of slot 22 and perpendicular thereto. Furthermore, the said ridge establishes a peripheral boundary for said gap 28, suchthat.

dowels 29 are shown in the forward face of com plementary member l2 which enter appropriate holes 38 in the other member 13. Said members accordingly cannot be rotated out of proper wave guide alinement as the clamping ring is screwed home.

In use, the structure described obtains a virtual electrical continuity for R. F. currents notwithstanding physical gap at the ends of substantially meeting wave guide sections 12 and i3. This is accomplished by use of the quarter-wave dimension of depth of gap perpendicular to the wave guide sections and in open communication with the longitudinal quarter-wave length deep slot 22. Considering the respective depths of gap and slot as di and d2 the complete depth of the two together will be A i-l' 2=' since and and where Ag is the wave guide wavelength. Slot 22 constitutes a quarter-wave shorted sectionopen at its forward end into gap 28 and will reflect a very high impedance there. This is then transformed to a very low impedance at place of entry of the gap into the wave guide, that is, between the ends of the walls of the wave guide where separated by said gap, and for the entire peripheral length of the gap. This impedance isalmostzero as a result of which the gap is electrically eliminated to radio frequency and the guided wave passes the junction of the wave guide sections with a minimum of reflection and hence with high efficiency of transfer. The angular disposition of gap 28 to slot 22 at a quarter wave-length distance from the remote ends of said. gap and slot presents a physical discontinuity at the point of highest impedance and thereby beneficially aids in maintaining a low impedance at the junction of the gap and the wave guide channel or passageway. Since the end of the slot 22 remote from gap 28 is closed,

and'since the slot 22 begins where the gap 23 ends, the slot and gap together constitute a blind alley of which the gap is half the length and the slot is the other half of the length, and the angular discontinuity is midway of the length of said blind alley, the full length thereof being half a wave length.

I claim:

7 1. A cavity coupling for instrumentalities having hollow passageways for conveying high frequency wave energy, comprising a pair of complementary substantially fiat-ended members, the fiat ends whereof are parallel with a gap spacing therebetween, said members providing a blind alley inclusive of said gap spacing, one of said members having a part projecting from the flat end thereof establishing both the width and radial extent of said gap spacing and constituting a discontinuity substantially midway of the depth of said blind alley, said gap spacing opening into said passageway and said blind alley having a dimension related to wave length of the high frequency and comprising means for establishing high frequency electrical continuity from one complementary member to the other.

2. A cavity coupling for instrumentalities having hollow passageways therein for conveying high frequency wave energy, comprising a pair of axially opposed complementary members neither one of which projects beyond the other, said members providing a gap .spacing between opposing ends thereof and providing a blind alley in part by said gap spacing between said members and in part within one of said members, the depth of said blind alley causing low impedance to exist across said gap spacing at the part of said members next the passageway between which a high frequency current flow is required.

3. A cavity coupling comprising complementary members each of which has an opening therethrough providingwalls alined in pairs defining a common passageway extending from one member into the other for transmission of wave energy, said members having generally flat faces near to and addressed toward each other, a ridge on one of the addressed fiat faces of said members, said ridge engaging the other addressed fiat face and providin a gap between the addressed faces of said members radiating from said passageway of the members to and limited in a radial direction by said ridge, and one of said members having a slot opening into said gap next said ridge.

4. A cavity couplingcomprising complementary members, means for holding said members together, said members providing walls alined in pairs defining a common passageway extending from one member into the other for transmission of wave energy lengthwise of said passageway, said members providing a gap peripherally of and opening into said passageway between said members, one of said members having a ridge disposed opposite to, in parallelism with and remote from said opening of the gap into said passageway, and one of said members having a slot transverse to said gap and communicating therewith next said ridge.

5. A cavity coupling comprising complementary members, means for holding said members together, said members providing walls alined in pairs defining a common passageway extending from one member into the other for transmission of wave energy lengthwise of said passageway, said members providing a gap peripherally of and opening into said passageway between said members, one of said members having a ridge disposed opposite to, in parallelism with, and remote from said opening of the gap into said passageway, one of said members having a slot transverse to said gap and communicating therewith next said ridge, the depth of said gap and of said slot having a, value by addition of half wave length referred to the opening.

6. A cavity coupling comprising a pair of complementary members of which one member consists of an inner body portion and an outer body portion, the inner body portion being substantially rectangular and having a rectangular opening therethrou-gh with the face of said inner body portion perpendicular to the opening having equal dimensions perpendicular to each side of the openingto the corresponding edge of the said body portion the second one of said complementary members overlying said face of the inner body portion of the first mentioned member in spaced relation thereto, thereby providing a gap between the said second complementary member and said face of the first said complementary member, and means provided by said outer body portion of the first mentioned complementary member peripherally of and radially beyond the edges of the inner body portion of the first mentioned complementary member in parallelism thereto confining said gap to also have equal dimensions perpendicular to each side of the opening, and means for retaining said members assembled.

7. A cavity coupling comprising a pair of complementary members of which one member consists of an inner body portion and an outer body portion, the inner body portion being substan tially rectangular and having a rectangular opening therethrough, and the outer body portion being substantially cylindrical with a rectangular opening receivingthe inner rectangular body portion therein, said body portions providing a slot peripherally therebetween of a depth less than the thickness of said body portions and opening at one face only of said body portions a third coupling member assembled with said pair of members and overlying the said face and end of said slot in spaced relation thereto, thereby providing a ap from the slot to the rectangular opening, and means at the end of said slot at its junction with said gap confining the gap to rectangular shape and equal dimensions perpendicular to each side of the rectangular opening, said third member having a circular outer edge, and a ring for securing said cylindrical outer body and said third member together.

ERNEST C. OKRESS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 579,643 Gleason Mar. 30, 1897 1,512,071 Whittington Oct. 21, 1924 1,610,414 Bernard Dec. 14, 1926 2,155,508 Schelkunofi Apr. 25, 1939 2,174,963 Braaten Oct. 3, 1939 2,190,668 Llewellyn Feb. 20, 1940 2,286,952 Cannon June 16, 1942 2,291,070 Bruno July 28, 1942 2,351,895 Allerding June 20, 1944 2,401,344 Espley June 4, 1946 2,402,540 Espley June 25, 1946 2,407,318 Mieher Sept. 10, 1946 FOREIGN PATENTS Number Country Date 503,467 Great Britain Apr. 6, 1939 

